MANAMA, Bahrain — Bahrain's Ministry of Interior says an explosion west of the Gulf island nation's capital of Manama has wounded two policemen.

The ministry reported the blast, which happened late on Thursday, on its official Twitter account. It says the explosion took place in the area of Karrana. It provided no further information on the cause of the explosion.

Later, police blocked and shut a major highway in the area for traffic.

Bahrain, a Western-allied kingdom that is home to the U.S. Navy's 5th Fleet, has faced four years of unrest following widespread anti-government protests led by the country's Shiite majority against its ruling Sunni monarchy.

Young protesters routinely clash with riot police. A number of small bombs mainly targeting security forces have killed and wounded police officers.